The invention relates to a vibration damper, comprising a cylinder with an axis, a piston rod passing movably in an axial direction through at least one cylinder end, a piston being connected inside the cylinder to the piston rod, a plurality of fluid chambers variable in capacity and in relation to one another as a function of the movement of the piston rod relative to the cylinder and fluid connections between at least two of the fluid chambers, wherein at least one of the fluid connections comprises a shut-off valve assembly between two sections of this fluid connection, and wherein the shut-off valve assembly is constructed with at least one valve seat adjacent to which there is a first section, and wherein further a first side of a valve shut-off element can be pressed resiliently against the valve seat into a shut-off position for the first section, and wherein further a second side of the valve shut-off element remote from the first side of the valve shut-off element, adjacent a control chamber can be subjected to the action of the fluid pressure in this control chamber, wherein the control chamber is connected to the first section via a throttle section which passes through the valve shut-off element and wherein furthermore the control chamber communicates with the second section via a control chamber outlet, and wherein an outlet cross-section dimensioning means is associated with this control chamber outlet, and wherein the outlet cross-section dimensioning means is adjustable to a plurality of positions which respectively condition various outlet cross-sections of the control chamber outlet.